Handheld computational device having securing elements

ABSTRACT

In another aspect, a handheld electronic device is disclosed that includes a body sized and shaped for holding by one hand of a user. The device further includes a user interface comprising a plurality of buttons for operating the device and at least one securing element coupled to the body. The securing element is adapted for engagement with at least one digit of the user&#39;s hand to facilitate holding the device so as to allow the user to operate the device, via its user interface, with one or more other digits of that same hand. In some embodiments, the device can be utilized for calculating a variable value associated with a loan (e.g., monthly payment) based on entered values of the other variables of the loan (e.g., amount, interest rate, and duration).

BACKGROUND OF THE INVENTION

The present invention relates generally to computational devices, andmore particularly, to handheld computational devices having an enhanceduser interface that facilitates performing mathematical computations.

The purchase of a real-estate or a personal property (e.g., a house (orother real-estate) or a car) typically requires obtaining a loan forfinancing the transaction. An individual who faces such a prospect maydesire to know the requisite monthly payment associated with a loanborrowed at a prevailing interest rate for a given loan duration.Moreover, such an individual may need to compare monthly payments forloans having different interest rates and/or durations. Alternatively,or in addition, such an individual may desire to know a maximum pricethat she can afford based, for example, on her income. In other cases,an investor may need to quickly calculate the return on money investedat a given interest rate.

Traditionally, mortgage calculations could be performed by reference totables that provided a compilation of a set of discrete valuescorresponding to variables involved in a mortgage computation. The useof such tables, however, is cumbersome. Further, one may need tointerpolate between the tabulated values to arrive at the value of adesired variable. With the advent of digital calculators, suchcomputations can be performed by programming a calculator. However, suchprogramming of digital calculators is not only beyond the scope ofexpertise of many individuals, who may not even know the properequations to program, but it can also be very time-consuming. Morerecently, a variety of mortgage calculators can be found on theInternet. However, the use of such calculators require having access notonly to a computer but also to the Internet. As such, they can typicallybe utilized only in an office setting or at home. More significantly,such mortgage calculators generally provide a limited functionality(e.g., they only allow calculating the monthly payment associated with aloan).

Accordingly, there is a need for enhanced computational devices that canbe readily utilized in different settings to perform computations, suchas those typically required for assessing financial implications ofobtaining a loan (e.g., for buying real-estate) and/or investing money.

There is also a need for such computational devices that can be employedby a variety of individuals with minimal training.

SUMMARY OF THE INVENTION

In one aspect, the invention provides a computational device thatcomprises a processor for performing mathematical computations, and auser interface. The user interface comprises a display and a pluralityof functional buttons each associated with one of a plurality ofvariables in a mathematical equation defining a relationship among thosevariables. That is, the selection of any of the buttons informs thedevice that the user desires to calculate a value for a variablecorresponding to that button, based on the known values of the othervariables. In response to the selection of any of the buttons by a user,the processor effects presentation of one or more prompts in the displayto invite the user to enter values for variables associated with buttonsother than that selected by the user, and upon entry of the lastvariable value, the processor calculates a value for the variableselected by the user and presents said calculated value in the display.

In a related aspect, the mathematical equation provides the followingrelation among four variables of a loan equation:

$P = \frac{L*\left( \frac{R}{100*12} \right)}{1 - \frac{1}{\left( {1 + \frac{R}{100*12}} \right)^{({12*Y})}}}$wherein L denotes the loan amount, P denotes the monthly payment, Ydenotes the loan duration (in years), and R denotes the annual interestrate represented as a percentage value (this equation is based on theassumption that the interest is compounded monthly).

In another aspect, the mathematical equation comprises areturn-on-investment (ROI) equation defining a relation betweenvariables corresponding to an initial investment value, an interestrate, an investment duration and an appreciated investment value.

In a related aspect, the handheld computational device comprises amemory module for storing instructions for performing the abovefunctionality of the device. For example, the instructions can allowcomputing a value of each variable of the mathematical equation based onentered values of the other variables. In some cases, the instructionsare stored in a firmware.

In one aspect, the present invention provides a computational device,preferably handheld, that includes a processor and a user interface. Theuser interface can comprise a display, e.g., an LCD, and n functionalbuttons/keys, each of which is associated with a variable in amathematical equation defining a relation among n variables, whereinn>=2. Any (n−1) subset of those buttons can be selected to enter valuescorresponding to variables associated therewith in the display. Theremaining n^(th) button can then be selected to cause the processor tocalculate a value for the variable corresponding to the n^(th) buttonbased on the mathematical relation and the entered values of the othervariables, and to effect presentation of that calculated value in thedisplay.

The terms “buttons” and “keys” are used herein interchangeably, andgenerally refer to selection elements (e.g., hard-wired and/orimplemented in software) that allow a user to communicate with thedevice, e.g., select variables, enter values for those variables, oreffect presentation of a variable value in the display. For example, insome implementations, the selection of a button by a user signals to thedevice that the user is interested in obtaining a value for a variableassociated with that button in terms of known values of the othervariables, which can be input into the device by the user, e.g., inresponse to a series of prompts presented by the device to the user.

In a related aspect, in the above handheld device, each button can bemarked by a textual, a graphical or a combined textual/graphicalindicator that informs a user of the variable with which that button isassociated.

Alternatively, the display can present, for each button, a textual, agraphical and/or a combined textual and graphical indicator in a portionthereof in proximity of the button to inform a user of the variableassociated with that button. The indicator can further prompt the userto enter a value for its associated variable.

In another aspect, the handheld device can include a keypad comprising aplurality of numerical keys that can be employed for entering values ofthe variables associated with the aforementioned buttons.

In a related aspect, the handheld device can be implemented to allow auser to obtain the value of any of the four variables of the followingloan equation based on entered values of the other three:

${P = \frac{L*\left( \frac{R}{100*12} \right)}{1 - \frac{1}{\left( {1 + \frac{R}{100*12}} \right)^{({12*Y})}}}},$wherein L denotes the loan amount, P denotes the monthly payment, Ydenotes the loan duration (in years), and R denotes the annual interestrate represented as a percentage value (this equation is based on theassumption that the interest is compounded monthly).

In another aspect, a handheld computational device is disclosed thatincludes a processor and a user interface having n buttons (n≧2), eachof which is associated with a display portion. Each button correspondsto a variable in a mathematical equation that defines a relation among nvariables, wherein any (n−1) of the buttons can be selected to entervalues for corresponding variables in their respective display portions.Subsequently, the remaining n^(th) button can be selected to cause theprocessor to calculate a value of the variable corresponding to then^(th) button based on that mathematical relation and the entered valuesof the other variables. The processor can then effect the presentationof the calculated value in a display portion associated with said n^(th)button. In some embodiments, the device provides the last entered valueof a variable as a default value of that variable upon selection of abutton associated with that variable in a subsequent computationalsession. The user can change that default value, if needed.

The above handheld device can further comprise memory for storinginstructions for computing a value for any of the n variables from saidmathematical relation, based on values entered for the other (n−1)variables. In some embodiments, these instructions are stored infirmware.

In other aspects, the invention provides a handheld computational devicethat comprises a processor for performing mathematical computations aswell as a user interface. The user interface comprises a plurality ofselectable elements each associated with one of a plurality of variablesin a mathematical equation that defines a relationship among thosevariables. The user interface can further include a display having aplurality of segments, e.g., logical segments, each of which isassociated with one of those elements such that selecting that elementallows entry of a numerical value for a respective variable in thatdisplay segment or effects presentation of a numerical value calculatedby the processor, based on the mathematical relation andpreviously-entered values of the other variables, in that segment.

In yet another aspect, the invention provides a handheld computationaldevice that comprises a processor for performing mathematical operationsand a user interface that comprises n buttons and a plurality of displayportions. Each button is associated with one of the display portions andeach button corresponds to a variable in a mathematical relationcontaining n variables, each of which is defined based on values of theothers. The handheld device is configured such that the selection of any(n−1) subset of those buttons allows entry of values corresponding totheir associated variables in respective display portions thereof. Uponentry of those (n−1) variable values, the n^(th) button can be selectedto effect calculation by the processor of the value corresponding to theremaining n^(th) variable, based on the mathematical relation and theentered values of the other variables. The processor further effects thedisplay of the calculated value in the display portion associated withthe n^(th) variable.

In yet another aspect, the invention provides a graphical user interfacethat comprises n selectable elements (e.g., graphical elements) eachassociated with a variable in a mathematical relation that defines arelationship among n variables, wherein n≧2. The interface furtherincludes n display windows each corresponding to one of the elements,wherein any (n−1) of those elements can be selected to enter values forvariables associated with those elements. The remaining n^(th) elementcan then be selected to cause display of a value corresponding to thevariable associated with that n^(th) element in a display windowcorresponding thereto. The displayed value of the n^(th) element iscomputed based on the mathematical relation and values previouslyassigned to the other variables.

In another aspect, a computational device is disclosed that comprises aprocessor, and a user interface. The user interface includes a displayand a plurality of functional buttons each associated with one of aplurality of variables in an equation defining a relation among anamount of a loan, the loan duration, an interest rate of the loan, and aperiodic payment for paying off the loan. The interface provides threeadditional buttons one of which is associated with entry of a startdate, another with entry of an end date of the loan, and the third withentry of a date at which a pay-off amount of the loan is desired.Another button is provided in the interface that is associated withcalculating the pay-off amount of the loan at a given date. In responseto selection of the button associated with the pay-off amount, andsubsequent to entry of relevant parameters of the loan, the processorcalculates the pay-off amount and causes its presentation in saiddisplay.

In another aspect, a handheld electronic device is disclosed thatincludes a body sized and shaped for holding by one hand of a user. Thedevice further includes a user interface comprising a plurality ofbuttons for operating the device and at least one securing elementcoupled to the body. The securing element is adapted for engagement withat least one digit of the user's hand to facilitate holding the deviceso as to allow the user to operate the device, via its user interface,with one or more other digits of that same hand. In some embodiments,the securing element can comprise a sleeve coupled to a surface of thedevice body, e.g., a back surface, that is adapted for insertion of atleast one digit of the user's hand therein. In another embodiment, thesecuring element can comprise at least a groove formed in a surface ofthe device body to provide a frictional fit with a digit of a user'shand. In yet another embodiment, the securing element can comprise ahook-and-loop fastener for coupling a portion of the user's hand to thedevice body while leaving at least one digit of that hand (e.g., thethumb) free for operating the device.

By way of example, in a related aspect, two indentations are formed onthe back surface of the handheld computational device in each of which arod is disposed, preferably substantially flush with the back surface. Ahook-and-loop fastener is then coupled at each end to one of the rods.In another case, a recessed well is formed on a back surface of thedevice, and a rotationally adjustable cuff is provided that surroundsthe perimeter of the well substantially flush with the back surface. Tworods can be coupled to the cuff, and a hook-and-loop fastener can extendbetween the rods.

Further understanding of the invention can be obtained by reference tothe following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic top view of a computational device according tothe one embodiment of the invention,

FIG. 1B is a perspective view of the device of FIG. 1A,

FIGS. 1C-1H schematically depict an exemplary use of the device of FIGS.1A and 1B for calculating the monthly payment associated with aloan/mortgage obtained at a given interest rate and for a givenduration,

FIG. 2A is a schematic top view of a computational device according toanother embodiment of the invention,

FIGS. 2B-2E schematically depict an exemplary use of the device of FIG.2A for calculating the monthly payment associated with a mortgage/loanobtained at a given interest rate and for a given duration,

FIG. 3 illustrates an exemplary system architecture suitable forproviding the functionalities of computational devices according to theteachings of the invention,

FIG. 4A is a schematic top view of a computational device according toanother embodiment of the invention,

FIG. 4B schematically depicts that the user interface of the device ofFIG. 4A,

FIG. 5A is a schematic top view of a computational device according toyet another embodiment of the invention,

FIG. 5B is a schematic top view of a computational device according toanother embodiment of the invention,

FIG. 6 schematically depicts another embodiment of a computationaldevice in accordance with the teachings of the invention,

FIG. 7A is a schematic top view of a computational device in accordancewith another embodiment of the invention,

FIG. 7B is a schematic top view of a computational device in accordancewith yet another embodiment of the invention,

FIG. 8A is a schematic top view of a computational device in accordancewith another embodiment of the invention that allows performingreturn-on-investment calculations,

FIG. 8B is a schematic top view of a computational device in accordancewith another embodiment of the invention presenting a visual indicatorin its display to inform a user that the device is operating in acomputational mode in which the unit of years is employed for durationof a loan,

FIG. 8C is a schematic top view of a computational device in accordancewith another embodiment of the invention presenting a visual indicatorin its display to inform a user that the device is operating in acomputational mode in which the unit of months is employed for durationof a loan,

FIG. 8D is a schematic top view of a computational device in accordancewith another embodiment of the invention having a keypad with anarrangement of numerical keys that corresponds to that employed inphones,

FIG. 9 schematically depicts a handheld computational device accordingto one embodiment of the invention that is sized and shaped for holdingby a single hand of a user,

FIG. 10 schematically depicts a back surface of another handheldembodiment of a computational device of the invention having a pluralityof grooves on that back surface for providing a frictional fit for twodigits of a user's hand for a secure grip of the device while allowingthe user to employ other digits of that hand for operating the device,

FIG. 11 schematically depicts a back surface of a handheld embodiment ofa computational device of the invention having two sleeves on a backsurface thereof that allow securely holding the device by two digits ofone hand while utilizing one or more of the other digits for operatingthe device,

FIG. 12A schematically depicts the back surface of an embodiment of acomputational device according to the teachings of the invention havinga hook-and-loop fastener that allows holding the device andsimultaneously operating it with one hand,

FIG. 12B schematically depicts that the device of FIG. 12A can be heldvia engagement of one or more digits of a user with the hook-and-loopfastener,

FIG. 13 schematically depicts a back surface of another handheldembodiment of a computational device of the invention having ahook-and-loop fastener on a back surface thereof that is attached to arotatable adjustable cuff for engaging with one or more digits of a userhand for securely holding and simultaneously operating the device by onehand,

FIG. 14 schematically depicts a computational device in accordance withanother embodiment of the invention that allows a user to calculate thepay-off amount of a loan prior to its end date,

FIG. 15 schematically depicts a computational device in accordance withanother embodiment of the invention that provides a calendar in its userinterface,

FIG. 16 schematically depicts a computational device in accordance withanother embodiment of the invention that allows a user to calculate asum of interest payments made for a loan at any desired date during thelife span of the loan, and

FIG. 17 schematically depicts a computational device in accordance withanother embodiment of the invention that allows a user to storeinformation regarding a number of loan, e.g., by assigning a tag to eachloan.

DETAILED DESCRIPTION

The present invention provides computational devices, preferablyhandheld, that allow a user to readily obtain the value of any variableof a mathematical relation, which defines a relationship among aplurality of variables, based on entered values of the other variables.In many embodiments discussed below, various features of such devices ofthe invention, and in particular their user interface, are described byreference to a hand-held implementation that can be utilized as amortgage calculator. It should, however, be understood that theteachings of the invention are not limited to mortgage calculators, butare equally applicable to any computational device that can allowobtaining a value for a variable of a mathematical relation based onvalues assigned to the other variables of that relation. For example, acomputational device according to the teachings of the invention can beemployed in connection with loans having simple or compound interests(e.g., to determine a required monthly payment for a loan based on theinterest rate, the amount, and the duration of the loan). Further,although in many of the following embodiments, handheld implementationsof exemplary computational devices of the invention are discussed, thecomputational devices of the invention can also be implemented asdesktop devices.

With reference to FIGS. 1A and 1B, an exemplary handheld computationaldevice 10 in accordance with one embodiment of the invention is suitablefor calculating any of the following four variables of the loan/mortgageequation below (Eq. 1) based on the entered values of the others. Thesefour variables comprise: a loan amount (AMT) designated as L, a monthlymortgage payment (PMT) designated as P, a lending period in years (YRS)designated as Y, and annual interest rate (%) designated as R:

$\begin{matrix}{P = \frac{L*\left( \frac{R}{100*12} \right)}{1 - \frac{1}{\left( {1 + \frac{R}{100*12}} \right)^{({12*Y})}}}} & {{Eq}.\mspace{14mu} 1}\end{matrix}$wherein the above equation is based on the assumption that the interestis compounded monthly (this is reflected by the factor 12 in theequation). The factor 100 in the above equation is employed to convertthe value of the interest rate entered by a user as a percentage valueinto a decimal representation. It should be understood that the aboveequation can be readily modified to be based on a different temporalcycle for compounding the interest, or to accommodate the entry of theinterest rate in a decimal representation.

Although the above relation is presented as defining the monthly paymentvariable (P) in terms of the others, those having ordinary skill in theart appreciate that the above relation can be manipulated algebraicallyin a manner known in the art to define any of the other variables (i.e.,loan amount, lending period, or interest rate) based on values assignedto the remaining three variables. By way of example, the followingequation (Eq. 2) defines the loan amount (AMT) in terms of the othervariables:

$\begin{matrix}{L = {\frac{P*100*12}{R}*\left( {1 - \frac{1}{\left( {1 + \frac{R}{100*12}} \right)^{12*Y}}} \right)}} & {{Eq}.\mspace{14mu}(2)}\end{matrix}$

The exemplary device 10 (herein also referred to as a mortgagecalculator) includes a user interface 12 that comprises a display 14 andfour functional buttons/keys 16 a, 16 b, 16 c, and 16 d, hereincollectively referred to as buttons 16, each of which is associated withone of the above variables (i.e. monthly loan payment, loan amount,interest rate, and lending period).

The exemplary interface 12 further includes a keypad 24 comprising aplurality of numerical keys that allow assigning values to theaforementioned variables and presenting the assigned values in thedisplay 14. An ENTER key provided in the interface can then be employedto pass the assigned values to a processing element of the device, asdiscussed further below. The exemplary device 10 is also equipped withfunctionality for performing basic mathematical operations (i.e.,addition, subtraction, division and multiplication). That is, inaddition to a dedicated mortgage calculator, the exemplary device canalso be employed as a general-purpose calculator. More specifically, theexemplary device 10 includes a plurality of operational keys 26 thatprovide the required interface for performing such operations in aconventional manner. Moreover, the buttons for performing mathematicaloperations can be employed to facilitate the entry of numerical valuesfor variables of the above mortgage equation (or other mathematicalequations in alternative embodiments). For example, as discussed in moredetail below, in response to a prompt from the device to enter a valuefor a variable (e.g., the loan amount), a user can enter a series ofnumerical values separated by one or more of the “+”, “−”, “×” and/or“÷” buttons to cause pairwise addition, subtraction, multiplicationand/or division of those values such that upon pressing the ENTER key,the resultant value is assigned to the variable (such an entry of aseries of numerical values before the first invocation of the ENTER keyor between two successive invocations of the ENTER key is hereinreferred to as a “sub-session”). For example, rather than entering asingle value for the loan amount, a user can employ the “−” sign tosubtract costs associated with obtaining the loan from a nominal loanamount to obtain an effective value of the loan amount (i.e., the amountthat is actually accessible to the user for the purchase of a personalor a real-estate property). Further, a key labeled “On/C” allowsclearing numerical values entered during a subsession (e.g., afterpressing the ENTER key), as well as switching on the device. Another keylabeled “CE” allows clearing the last numerical value that was entered.In some embodiments, the computational device automatically shuts off ifno keys are pressed for a selected time period (i.e., after apre-defined time-out period). In some cases, before the shut-off, thedevice saves the values entered during the last session and hence allowsa user to continue a previously-initiated computation upon switching onthe device.

In this exemplary embodiment, each button can be selected by a user toinform the device that the user is interested in obtaining a valueassociated with that button. In response to such a selection, thecomputational device prompts the user to enter values for the otherthree variables, in a manner discussed in more detail below. Uponentering a value for the last of those three variables, the devicedisplays in the display 14 the value of the variable selected by theuser (i.e., the initially unknown variable). For example, the user canselect the button 16 a to indicate its interest in obtaining the valueof the monthly payment of a loan obtained at a given interest rate andfor a given duration. In response to the user's selection, the deviceprompts the user to enter, e.g., sequentially, the values of the otherthree variables (i.e., the loan amount, the interest rate (e.g., theannual interest rate) and the loan duration (e.g., in units of years)).Upon entering the last value, the device displays the value of themonthly payment, calculated, based on the values of the other threevariables, and by utilizing the above equation. As noted above, whenentering a variable value, the user can provide a series of numericalvalues and utilize the buttons for performing mathematical operations toobtain a resultant value based on those values, which can then beconveyed to the device by pressing the ENTER key. By way of example, auser can enter a nominal loan amount and subtract from that amount oneor more costs associated with obtaining the loan to arrive at aneffective loan amount. The effective loan amount can then be utilized,together with the loan duration and a monthly payment value, to obtainan effective interest rate for the loan (i.e., an interest rate thattakes into account not only the nominal loan amount but also costsassociated with securing the loan). By way of example, a user can employsuch a feature to compare different loans, which may have the samenominal interest rates but different effective interest rates due tovariations in costs associated with obtaining them.

In this exemplary embodiment, each button is labeled with a textualindicator to inform a user of the variable with which that button isassociated. More particularly, the button 16 a is labeled as “PMT”indicating that it is associated with the variable corresponding tomonthly payment. The buttons 16 b and 16 c are labeled as “AMT” and “%”to indicate their associations with variables corresponding to the loanamount and the annual interest rate, respectively. And the button 16 dis labeled as “YRS” to inform a user that it is associated with thevariable corresponding to the lending period (years). In thisimplementation, the association of a button and a variable indicatesthat the selection of that button would signal to the device the desireto calculate a value for that variable. In other embodiments, theassociation of a button with a variable indicates that the selection ofthe button allows entry of a value for that variable or that theselection of the button effects calculation and display of a value forthat variable based on previously-entered values of the other variables.

Although in this exemplary embodiment the buttons 16 are in the form ofsoftware-enabled hard buttons, in other embodiments the buttons 16 canbe in the form of programmable buttons (“soft” buttons) each of whichcan be programmed, either statically or dynamically, to provideassociation with a particular variable. Such soft buttons can provideadditional flexibility as they allow the reuse of the buttons fordifferent functions. For example, in an implementation of this exemplaryembodiment in which soft buttons are utilized, each button can bereprogrammed to change its variable association. The device 10 alsoincludes a solar cell, in addition to a battery (e.g., a rechargeablebattery), that provides power to the device.

As noted above, any of the four buttons 16 can be selected by a user toindicate the user's desire to calculate a value for the variableassociated with that button. Upon such selection, the device prompts theuser (e.g., by displaying textual and/or graphical indicators in thedisplay 14) to enter values for the other three variables, andcalculates and displays the value of the variable desired by the userbased on the entered values of the other variables. By way of example,in this exemplary embodiment, upon selection of the button 16 a (e.g.,by pressing the button), which corresponds to the monthly payment, thedevice can prompt the user (e.g., by displaying “LOAN AMT?:” in thedisplay 14) to enter a value of the loan amount, as shown schematicallyin FIG. 1C. The user can then employ the keypad 26 and the ENTER key toenter the value of the loan amount, e.g., 100,000 dollars as shown inFIG. 1D. Upon entry of the loan amount, the device prompts the user(e.g., by displaying “% ?:” in the display 14) to enter the value of theinterest rate, as shown in FIG. 1E. Upon entry of the interest ratevalue, e.g., an annual rate of 7.75% shown in FIG. 1F, the deviceprompts the user (e.g., by displaying “YRS?:” in the display 14) toenter a value for the loan duration, as shown in FIG. 1G. Once a valuefor the loan duration is entered, e.g., 30 years in this example, thedevice displays the value of the monthly payment (i.e., the value of thevariable initially selected by the user) calculated based on the abovemortgage equations and the entered values of the other variables, asshown in FIG. 1H. In this exemplary embodiment, the numerical value ofthe calculated monthly payment is presented in the display 14 togetherwith a descriptive indicator (“Monthly PMT?:”) to further help the userassociate the presented numerical value with the variable of interest.The user can then press the ENTER button to reset the device (to returnto the display shown in FIG. 1A) and start a new calculation, ifdesired.

It should be understood that a user of the device 10 can obtain a valuefor any of the other variables based on entered values of the otherthree in a similar manner. For example, a user who is interested inknowing a loan amount that corresponds to given values of the monthlypayment, interest rate and loan duration, can select the buttoncorresponding to the loan amount (e.g., the button 16 b in thisexemplary embodiment). Upon such selection, the device will prompt theuser, in a manner similar to that discussed above, to enter values forthe monthly payment, interest rate and duration of the loan. Once thesevalues are entered, the device calculates and displays the respectivevalue of the loan amount based on the entered values of the othervariables.

In other alternative embodiments, a user can enter values for the knownvariables by pressing buttons corresponding to those variables andemploying a keypad, and can subsequently select the button associatedwith the fourth variable (i.e., the unknown variable) to cause thedevice to calculate a value for that variable and to display thecalculated value.

For example, with reference to FIG. 2A, another embodiment of acomputational device 10′ according to the teachings of the inventionincludes a user interface 12′ that allows a user to enter values for anythree of the above variables in order to obtain the respective value ofthe fourth based on the above mathematical relation, in a mannerdiscussed in detail below. More specifically, the user interface 12′includes a display 14′ and four buttons/keys 16′a, 16′b, 16′c, and 16′d,herein collectively referred to as buttons 16′, each of which isassociated with one of the above variables (i.e., loan amount, monthlyloan payment, lending periods in years, and annual interest rate). Thatis, each button can be selected to enter a value corresponding to thevariable associated therewith in the display 14′ or to effectpresentation of a value corresponding to its associated variable, basedon previously-entered values of the other variables, in the display.

With continued reference to FIG. 2A, any three of the four buttons 16′can be selected, e.g., sequentially, to enter values corresponding totheir respective variables in the display 14′. The fourth button, i.e.,the button associated with the variable whose value is desired based onthe entered values of the others, can then be selected to effectpresentation of a value for the fourth variable in the display 14′,based on the above mathematical relation as well as the entered valuesof the other three variables.

For example, a user who is interested in determining the monthly paymentof a given mortgage/loan (e.g., 500,000) at a selected annual interestrate (e.g., 5%), and for a selected duration (e.g., 30 years) can employthe exemplary device 10′, and in particular its user interface, in thefollowing manner. By way of example, upon selecting (e.g., pressing) thebutton “AMT,” the user is prompted (e.g., by displaying “Loan AMT:”) toenter a value for the variable corresponding to the loan amount, asshown schematically in FIG. 2A. The user can then employ the numericalkeys 24′ to enter a desired value in the display (e.g., $500,000 asshown schematically in FIG. 2B), and select the ENTER key to submitentered value for that variable. In this exemplary implementation, thevalues of the variables are assumed to be in dollars (though otherdenominations and currencies can also be employed).

Upon subsequent selection of the button 16′d, the device prompts theuser to enter a value for the duration of the loan in years (e.g., bydisplaying LOAN YEARS: in the display 14′), as shown schematically inFIG. 2C. In this example, the user has chosen 30 years for the loanduration (in this implementation, it is assumed that the duration is interms of years, though other time durations can be implemented in otherembodiments). In a similar fashion, a value for the third variablecorresponding to the annual interest rate can be entered by selectingthe button 16′c, as shown in FIG. 2D. Subsequently, the buttonassociated with the fourth variable (that is, the variable for which novalue has been entered), which in this example is the button 16′aassociated with the monthly payment, can be selected to causepresentation of a value corresponding to that fourth variable, based onthe above mathematical relation (Equation 1) and the entered values ofthe other three variables (in this example: loan amount, interest rateand loan duration), as shown in FIG. 2E. As discussed in more detailbelow, the selection of the fourth button, in this case the button 16′a,can cause a processor of the device 10′ to calculate the value of thefourth variable and to effect its presentation in the display.

In the above example, the sequence by which the buttons corresponding tothe variables for which values are selected can be different than thatdiscussed above. In fact, those variable values can be entered in anydesired sequence. Moreover, the device 10′ can be utilized to calculatethe value of any variable (and not only the monthly payment discussedabove) based on entered values of the other three.

In some embodiments, upon selection of a button by a user to enter avalue corresponding to a variable associated with that button, a defaultvalue for that variable is presented in the display. The user has theoption of changing the default value by employing the numerical buttons,or can alternatively leave the default value unchanged. The defaultvalue can be, e.g., the value utilized for that variable in apreviously-performed calculation.

A variety of hardware and software architectures known in the art can beemployed to implement the functionality of the afore-mentionedcomputational devices 10 and 10′, including their user interfaces, aswell as other embodiments discussed herein. By way of example, as shownschematically in a system diagram 28 of FIG. 3, the device 10 caninclude a mathematical processing unit (mpu) of the type known in theart that can communicate with the display 14 and the above-describedbuttons/keys of the device's user interface (e.g., the buttons 16, thekeypad 24 and operational keys 26) via an I/O bus 34. The processingunit 30 is also in communication with a program memory 36 via a data bus38. The programming memory can store instructions for implementing theabove mortgage equation (or other equations) to obtain a value for anyof its four variables based on entered values of the other three. Avariety of processors can be employed in implementing the device 10.Some examples of such processors include, without limitation, “Saturn”processors marketed by Hewlett-Packard Company of Palo Alto, Calif.,U.S.A., and the family of “H8” microprocessors for embedded systemsmarketed by Renesas Technology America, Inc. of San Jose, Calif., U.S.A.

By way of example, upon selecting one of the buttons 16 (FIG. 1A)corresponding to a variable (e.g., the monthly payment) for which avalue is desired, the mpu 30 can cause the display 14 to present theuser with a number of prompts that invite the user to enter values forthe other three variables. More specifically, upon entering a value inresponse to one of the prompts, the mpu can cause the display to providethe user with the next prompt. In response to each prompt, the user canutilize the keypad 24 to transfer a value corresponding to the variableassociated with the prompt to the mpu 30.

Once the user enters the value of the last known variable (in responseto the last prompt), the mpu calculates the value of the desiredvariable, based on the above mortgage relation and the entered values ofthe known variables, and causes the display to present the calculatedvalue to the user. More specifically, the mpu can execute theinstructions, based on the above mortgage equation, stored in the memory36 to obtain a numerical value for the unknown variable. In someimplementations, four sets of instructions, each defining the value ofone of the variables of the above mortgage equation in terms of knownvalues of the other three, are stored in the memory 36. In response tothe selection of a variable by the user (via the user interface) forwhich a value is desired (i.e., in response to the selection of anunknown variable), the mpu determines (e.g., based on asoftware-implemented flag) which of the four instructions to executeonce the values of the other three variables are entered.

By way of another example, in the device 10′, upon selecting one of thebuttons 16′ (FIG. 2A), the mpu 30 effects presentation of a prompt onthe display inviting the user to enter a value of the variableassociated with that button. As discussed above, the user can thenutilize the numerical keys 24′ to transfer a numerical value for thatvariable to the mpu 30 that, in turn, effects presentation of that valueon the display and further stores that value in a register thereof.Values for two additional variables can be similarly transferred to themathematical processing unit 30. Subsequently, upon selection of thefourth button (i.e., the button associated with the fourth variable),the mpu 30 executes the instructions stored in the memory 36 to obtain anumerical value for the fourth variable. The mpu then effectspresentation of the value corresponding to the fourth variable in thedisplay 14.

The implementation of a computational device of the invention, and inparticular its user interface, is not limited to the embodimentdiscussed above. By way of example, FIG. 4A schematically depicts acomputational device 18 according to another embodiment of the inventionhaving a user interface 20 that includes a plurality of software-enabledhard buttons/keys 22 a, 22 b, 22 c and 22 d, herein collectivelyreferred to as buttons 22. In some implementations, a user guide thataccompanies the device includes instructions on how to programmaticallyalter the association of the buttons with the variables to which theycorrespond. Although in this implementation, the buttons themselves areunmarked, in other implementations they can be labeled with selecteddescriptive markings. For each button, the display 14 presents a textualindicator in proximity thereof (e.g., directly above it in thisexemplary embodiment) that informs a user of the variable with whichthat button is associated. In other embodiments, graphical or combinedgraphical and textual indicators can also be employed. For example, inthis embodiment, in a space directly above the button 22 a, the displaypresents “PMT” indicating that the button is associated with thevariable corresponding to the monthly payment. In a similar fashion, thedesignations “AMT,” “%,” and “YRS,” each of which is presented directlyabove one of the other buttons 22 b, 22 c and 22 d, inform a user of thevariables associated with those buttons.

The exemplary device 18 operates in a similar manner as that discussedabove in connection with the previous embodiment 10′. More specifically,upon selection of any of the buttons 22, the user is prompted to enter avalue for that button, as shown schematically in FIG. 4B for thevariable AMT. Once values for three of the variables are entered, thebutton associated with the fourth variable can be selected to cause thedisplay of its value, calculated based on the assigned values of theother three values. Alternatively, in some implementations, the device18 operates in a manner similar to that discussed in connection with thecomputational device 10 above. More specifically, in such animplementation, upon selecting one of the buttons 22, the device promptsthe user to enter values for variables associated with the other threebuttons. Upon entering the last value, the device calculates anddisplays the value of the variable associated with the selected buttonbased on the entered values of the other variables.

By way of another example, FIG. 5A schematically depicts anotherembodiment 40 of a computational device in accordance with the teachingsof the invention, which similar to the previous embodiments, can beutilized as a mortgage/loan calculator. More specifically, the device 40includes a user interface 42 comprising a plurality of buttons/keys 44a, 44 b, 44 c and 44 d, herein collectively referred to as buttons 44,and a plurality of display portions 46 a, 46 b, 46 c and 46 d. Eachbutton 44 is associated with one of the display portions 46 a-46 d. Thatis, upon selection of each button, a user can enter a value for thevariable associated with that button in a display portion correspondingthereto. Alternatively, the selection of a button can cause presentationof a value calculated for that button's associated variable, based onpreviously entered values of the other variables, in its respectivedisplay portion.

In the exemplary device 40, the association of each button with adisplay portion is conveyed to a user by placement of that buttonhorizontally adjacent to its respective display portion in substantialalignment therewith. In another embodiment 40′, depicted schematicallyin FIG. 5B, each button (44′a, 44′b, 44′c and 44′d) and itscorresponding display portion (46′a, 46′b, 46′c and 46′d) in the userinterface 42′ are vertically aligned in proximity of one another toconvey their association to a user. Additionally, a graphical indicator,e.g., in the form of an arrow, can be optionally provided to connecteach button to its associated display portion. For example, in thisembodiment, arrows 45 a, 45 b, 45 c and 45 d show, respectively,association of buttons 44′a, 44′b, 44′c and 44′d with display portions46′a, 46′b, 46′c and 46′d.

Referring again to FIG. 5A, the exemplary device 40 can be employed in asimilar manner as that described above in connection with the otherembodiments. For example, the buttons 44 a, 44 b, and 44 c can beselected to enter values for the variables corresponding to the monthlypayment (PMT), the loan amount (AMT), and the annual interest rate (%).Subsequently, the button 44 d can be selected to effect calculation of avalue for the loan duration (YRS), based on the entered values of theother three, and to effect its presentation in its corresponding displayportion 46 d. The device 40 can be similarly employed to obtain a valueof any of the other variables based on values assigned to the otherthree. Alternatively, in some implementations, the selection of one ofthe buttons can cause the device to prompt the user to enter values forvariables associated with the other buttons. In such an implementation,once the last value is entered, the device calculates the value of thevariable associated with the selected button and presents the calculatedvalue in the display segment corresponding to the selected variable.

With reference to FIG. 6, in another embodiment 48, rather thanproviding a plurality of distinct display portions (such as the displayportions depicted above in connection with the exemplary devices 40 and40′), a single display can be logically segmented such that each segmentwould correspond to one of a plurality of buttons that are, in turn,associated with the variables of the above loan/mortgage equation. Forexample, the exemplary computational device 48 according to thisembodiment of the invention comprises a user interface 50 that includesa display 52 having logical segments 52 a, 52 b, 52 c, and 52 d—thedashed lines in the figure are provided for illustrative purposes andare intended to indicate only logical and, not necessarily physical,distinctions among the segments—that are associated, respectively, witha plurality of buttons 54 a, 54 b, 54 c and 54 d, herein collectivelyreferred to as buttons 54. The buttons 54 a, 54 b, 54 c and 54 d are, inturn, associated with variables monthly payment (PMT), loan amount(AMT), annual interest rate (%), and duration of the loan (YRS).

Further, similar to the previous embodiment, a numerical keypad 56 aswell as an ENTER button are provided in the user interface that allow auser to enter values for the above variables in their respective displaysegments. Moreover, a clear button (“ON/C”) is provided that allowsclearing the display segments from previously-entered values. In someimplementations, selection of the clear button results in clearing theactive display segment (the segment being utilized at the time). In someother implementations, a separate “ON/C” button is provided for eachdisplay segment in order to allow clearing each display segmentindependently from the others.

In this embodiment, each button 54 includes a textual indicator thatinforms a user of the variable with which that button is associated. Theshown indicators are identical to those discussed above in the previousembodiments. For example, an indicator “PMT” that labels the button 54 ainforms the user that that button is associated with the monthly paymentvariable PMT. In other implementations, other textual or graphicalindicators or a combination thereof can be employed. Moreover, in someother implementations, rather than labeling the buttons themselves, eachlogical display segment can present an indicator (e.g., a textual orgraphical icon) that informs a user of the variable with which thatsegment's button is associated.

With continued reference to FIG. 6, similar to the previous embodiments,a user can readily employ the device 48 to calculate a value for any ofthe four variables (monthly payment, loan amount, annual interest rate,loan duration) by entering values for the other three. For example,selecting the button 54 b (AMT) allows the user to enter a value (e.g.,$500,000 in this example) for the amount of the loan in the displaysegment 52 b. The values of two other variables (e.g., monthly payment(PMT) and loan duration (YRS) in this example) can be entered in theirrespective display segments in a similar fashion (in this example,$3,000 and 30 years, respectively). Subsequently, the fourth button(e.g., the button 54 c in this example corresponding to the annualinterest rate) can be selected to effect presentation of the value ofthe variable associated therewith in its respective display segment 52 d(an interest rate of 6.00% in this example). Alternatively, in someimplementations of the device 48, upon selection of a buttoncorresponding to an unknown variable (i.e., a variable for which a valueis desired), the device can prompt the user, e.g., in a manner similarto that discussed in connection with the above embodiments, to entervalues of the other three variables. Once the last known variable valueis entered, the device calculates the value of the unknown variable anddisplays the calculated value in the respective logical display segment.

It should be understood that the units associated with the variables ofthe loan/mortgage equation that are presented above in discussingvarious embodiments are only for illustrative purposes and are notintended to imply that other units cannot be chosen. In fact, anydesired unit can be selected for any of the variables. For example, acomputational device of the invention can be readily configured toaccept a monthly interest rate, rather an annual rate, and/or accept theloan duration in terms of months, rather than years.

A loan/mortgage calculator according to the teachings of the invention,such as those described above, provides a number of distinct advantages.For example, it provides an easy-to-use interface that enables a user toreadily calculate any of the variables associated with the mortgageequation without a need to consult a manual or engage in programming acalculator, which can be time-consuming and is typically beyond theskill scope of many users. Moreover, in many embodiments, the symbolsfor identifying the functionality of various buttons are chosen to bereadily recognized as being associated with variables corresponding tothose buttons. For example, the symbol “AMT,” which is suggestive of“amount”, is employed to identify a loan amount. Further, the handheldimplementation of a mortgage calculator of the invention allows the userto readily carry it, e.g., in a shirt pocket. In addition, as discussedin more detail below, many handheld embodiments of a loan/mortgagecalculator of the invention are sized and shaped for holding andoperating with one hand of the user, thereby further enhancing its easeof use. Moreover, a loan/mortgage calculator of the invention allows auser to calculate any of the variables associated with the loan/mortgageequation by entering values of the others. For example, a user, e.g., aprospective real-estate buyer, can utilize the mortgage calculator todetermine the monthly payment associated with a loan characterized by anamount, an annual interest, and a duration. Alternatively, a user canemploy the loan/mortgage calculator to calculate, for a given monthlypayment and a given loan duration, the loan amount at the prevailinginterest rate. In other cases, a user may employ the calculator todetermine a loan duration, for given values of the interest rate,monthly payment and the loan amount, or to calculate the interest ratefor given values of the monthly payment, the loan amount and the loanduration. Further, a user can utilize the calculator to determine theeffective interest rate of a loan. This feature can be useful, e.g., forcomparing the effective interest rates associated with two or moreloans. For example, two loans having the same nominal amounts can havedifferent effective interest rates due to varying costs associated withobtaining those loans, e.g., origination fees, points, closing cost,attorney's fees, etc.

In other embodiments, additional functionality can be incorporated in acomputational device according to the invention so as to provide a userwith an augmented set of options. By way of example, FIG. 7 depictsanother handheld loan/mortgage calculator 58 according to a furtherembodiment of the invention that not only allows a user (e.g., aprospective house purchaser) to calculate values for each variable ofthe above loan/mortgage equation based on entered values of the otherthree, but also permits the user to determine a maximum loan/mortgageamount for which that user can qualify based, e.g., on user's yearlyincome.

More specifically, the exemplary computational device 58 includes a userinterface 60 that comprises a display 62, five buttons/keys 64 a, 64 b,64 c, 64 d, and 64 e, herein collectively referred to as buttons 64, anumerical keypad 66 including an ENTER key that allows entry of valuesfor variables associated with the buttons 64 and an “ON/C” key forclearing the display. The buttons 64 a, 64 b, 64 c and 64 d areassociated, respectively, with the monthly payment, the amount of loan,the annual interest rate and the duration of the loan (in years) in amanner similar to that discussed above in connection with the previousembodiments. The additional button 64 e allows the user to enter a valuefor the user's income, e.g., the user's salary.

The exemplary computational device 58 can be utilized in a mannersimilar to that described above to compute any of the variables of theloan/mortgage equation based on values of the other three. In addition,a user can utilize the device 58 to determine the amount of a loan forwhich that user is qualified in the following manner. The user can entervalues for the interest rate and the loan duration as well as an income(e.g., yearly salary) (by selecting buttons associated with thesevariables and utilizing the keypad 66, e.g., in a sequential manner).Subsequently, the user can select the button 64 b to cause the device topresent in the display 62 a maximum amount of a loan for which the userqualifies. By way of example, many lending agencies require that themonthly payment associated with a loan be at most equal to one-third ofan applicant's monthly gross (before tax) income. For such a case, thedevice can be programmed to calculate the user's monthly income from theentered value of the yearly income. The maximum loan amount for whichthe user qualifies can then be computed by utilizing one-third of themonthly income, or another known default value such as 25% of theincome, as the value for the monthly payment, together with thepreviously-entered values of the interest rate and loan duration, in theabove mortgage equation. In other words, the maximum loan amount forwhich a user can qualify can be obtained from the following relation:

$\begin{matrix}{L = {\frac{\frac{INC}{3}*100}{R}*\left( {1 - \frac{1}{\left( {1 + \frac{R}{100*12}} \right)^{Y*12}}} \right)}} & {{Eq}.\mspace{14mu}(3)}\end{matrix}$in which L denotes the maximum loan amount, R denotes the annualinterest rate, INC denotes the user's annual income, and Y denotes theloan duration (in years). This equation is based on the assumption thatthe interest is compounded monthly. This equation can be readilymodified as known in the art to account for other temporal cycles forcompounding the interest.

In some implementations, the device is initially configured with adefault value corresponding to the fraction of the monthly income thatwould correspond to the maximum monthly payment (e.g., one-third in theabove example). The user can then be provided with instructionsregarding how to program the device to alter that default value.

Alternatively, in some implementations of the device 58, upon selectingthe button 64 b, the device can prompt the user to enter values for themonthly payment, interest rate, loan duration and the user's income.Once these values are entered, the device can calculate a value of themaximum loan amount for which the user is qualified, and can display thecalculated amount in the display 62, e.g., together with a descriptiveindicator (e.g., “AMT:”).

In some cases, an individual may need to know the maximum price of areal-estate (e.g., a house) that she could afford given her annualincome and a down payment, and a selected annual interest rate. Anembodiment 68 of a computational device of the invention, depictedschematically in FIG. 7B, allows performing such a calculation, inaddition to loan/mortgage calculations discussed above. Morespecifically, it includes an interface 70 with a display 72 and sevenbuttons 74 a, 74 b, 74 c, 74 d, 74 e, 74 f, and 74 g, hereincollectively referred to as buttons 74. The buttons 74 a (monthlypayment), 74 b (loan amount), 74 c (annual interest rate) and 74 d (loanduration) can be utilized in a manner similar to that described inconnection with the previous embodiments to perform loan/mortgagecalculations.

The additional buttons 74 e, 74 f and 74 g allow a user to determine themaximum price of a real-estate that she can afford based on her incomeand a down payment. The button 74 e is associated with a variablecorresponding to the maximum real-estate (e.g., house) price, and thebuttons 74 f and 74 g relate, respectively, to the values of income anddown payment.

Upon entering the values for income and down payment by selecting thebuttons 74 f and 74 g, respectively, the user can select the button 74 eto cause the exemplary device 68 to present the maximum real-estatevalue that the user can afford. More specifically, the device 68calculates the maximum loan amount for which the user is qualified andadds that value to the entered value of the down payment to arrive atthe maximum real-estate value. The device then presents the calculatedmaximum real-estate value in the display 72.

In yet further embodiments, a computational device of the invention,preferably in a handheld implementation, can be employed to obtain areturn on a given investment at a selected interest rate. By way ofexample, such a computational device can be utilized to readilycalculate the return on money invested in a bond or acertificate-of-deposit that provides a guaranteed interest rate over itslife time (i.e., over a fixed time period). FIG. 8A schematicallyillustrates an exemplary embodiment of such a computational device 76that comprises a user interface 78 having a display 80, four buttons 82a, 82 b, 82 c, and 82 d, as well as a keypad 84. The button 82 a(labeled “INV” in this embodiment) is associated with an initialinvestment (e.g., money needed to buy a bond), while the buttons 82 band 82 c relate, respectively, to the interest rate and the duration ofthe investment. In this exemplary embodiment, the interest rate isassumed to be an annual rate, though other units (e.g., semi-annual) canalso be employed. In this implementation, the button 82 c allows theuser to identify a time cycle (e.g., number of months) over which theinterest is compounded (e.g., semi-annual, annual). In otherembodiments, a default cycle (e.g., annual) can be utilized, and thebutton 82 c can be eliminated. Further, the button 82 d is associatedwith the return-on-investment (ROI) variable.

A user can enter values for the initial investment, interest rate,duration of the investment, as well as the compound cycle by selectingthe buttons associated with these variables. Subsequently, the selectionof the button 82 d can effect the display of the ROI value in thedisplay 80. More specifically, the device can utilize the followingwell-known equation for calculating compound interest to calculate thefuture value of the present investment at the given values of annualinterest rate, investment duration and compound cycle (number of timesper year interest is compounded):

$\begin{matrix}{{FV} = {{PV}\left( {1 + \frac{R}{N}} \right)}^{y*N}} & {{Eq}.\mspace{14mu}(4)}\end{matrix}$in which FV refers to the future value of investment, R refers to anannual interest rate, N denotes the compound cycle and Y denotes theinvestment duration (in units of years in this example).

Similar to the above embodiments, the device 76 can include a systemarchitecture, such as that shown in FIG. 3, in which the necessaryinstructions (computer code) is loaded to calculate the future value ofthe investment based on the above equation. In some embodiments, thisfuture value can be displayed to the user. Alternatively, the value ofthe initial investment can be subtracted from the calculated futurevalue to obtain a return-on-investment value to be displayed to theuser.

The above device can be used, for example, by a loan officer of a bankto calculate the ROI associated with a loan extended to a customer at agiven interest rate. Alternatively, it can be employed by an individualto determine the ROI on buying a certificate-of-deposit. Other uses areapparent to those having ordinary skill in the art.

In some embodiments, a visual indicator is presented in the display toindicate a unit (e.g., years or months) associated with the duration ofa loan (or an investment), entered by a user or computed by the device.By way of example, FIG. 8B schematically shows such a visual indicator81 (in the form of letter ‘Y’) presented in the display of acomputational device according to one embodiment of the invention toinform a user that the device is operating in a computational mode inwhich the unit of years is employed for duration of a loan. In someembodiments, a user can alter the unit associated with the duration of aloan (or an investment) by pressing a pre-defined sequence of buttons(an instructional manual accompanying the device can inform a user ofthe sequence). For example, FIG. 8C presents a visual indicator 83 (inthe form of letter ‘M’) to indicate that the device is operating in analternative computational mode in which the unit of months is employedfor duration of a loan.

In some embodiments of the invention, the arrangement of the numericalkeys in the keypad can be different than that discussed above inconnection with the previous embodiments. By way of example, FIG. 8Dschematically depicts a computational device 85 in accordance withanother embodiment of the invention that includes a numerical keypad inwhich the numerical keys are arranged such that the lower numbers are onthe top and the higher numbers are on the bottom. Such an arrangement ofthe numerical keys may be advantageous to some users who utilizedevices, such as telephones, having such keypads, more often than theyuse conventional calculators having a keypad in which the numerical keysare arranged in a manner similar to that discussed in connection withthe previous embodiments.

As noted above, many embodiments of a computational device of theinvention are handheld to allow their easy portability and use.Moreover, in some preferred embodiments, the computational device issized and shaped for holding and operating by a single hand of anoperator. For example, FIG. 9 schematically depicts an exemplarycalculator 86 that can be not only held but also operated by a singlehand of a user. For example, the user can hold the calculator againsther palm via four fingers of her hand and utilize her thumb to pressvarious buttons to perform a desired computation, e.g., in a mannerdiscussed above.

In some embodiments, not only the calculator is sized and shaped forholding and operating by one hand, but it can also include securingelements coupled to its body that can engage with one or more fingers ofthe user's hand to facilitate its grasp by the user. By way of example,FIG. 10 schematically depicts an exemplary calculator 88 according tosuch an embodiment of the invention that includes two grooves 90 and 92are provided on a back surface 94 its housing that provide a frictionalfit for two fingers of a user's hand for secure grip of the calculator'sbody. FIG. 11 shows an alternative embodiment 96 in which two sleeves 98and 100 are coupled to a back surface 102 of its housing into which twodigits of a user's hand can be inserted to securely hold the calculatorin one hand while simultaneously operating it (in some embodiments, onlyone sleeve can be provided). In some embodiments, the sleeves can bemade of soft elastic materials, such as those commonly utilized forforming sport gloves. Further, in some embodiments, each sleeve (or someof them) can have not only an opening at one end through which a fingercan be inserted into sleeve but can also include an opening at the otherend that allows the tip of the finger to be exposed (not covered).

In yet another embodiment, shown schematically in FIG. 12A, acomputational device 104 of the invention can include a hook-and-loopfastener (e.g., Velcro™) 106 on a back surface 108 of its housing thatallows attaching the device to a user's hand while leaving one morefingers of that hand free for operating the device. More specifically,the back surface 108 includes two indentations 110 and 112 in whichcylindrical rods 114 and 116 are, respectively, disposed such that eachrod is substantially flush with the back surface 106. The Velcro™ ribbon106 can be secured to the device by wrapping one end thereof around oneof the rods and its other end around the other rod. As shownschematically in FIG. 12B, in use, the ribbon 106 can wrap around onerod, traverse over two (or more) fingers of a user's hand and wraparound the other rod, thereby securing both fingers to the back surface108 to facilitate holding the device while allowing the user tosimultaneously operate the device (e.g., perform data-entry) byutilizing the thumb of that hand. One advantage of such a hook-and-loopfastener is that it can be adjusted once for a particular user, andsubsequently be utilized by that user with a need for furtheradjustments (that is, it can provide custom-fitting for differentusers).

With reference to FIG. 13, in another embodiment 118, a back surface 120includes a recessed circular well 122 and a rotationally-adjustable cuff124 that surrounds the well. Two cylindrical bars 124 and 126 coupled tothe cuff, which are substantially flush with the back surface 120, allowsecuring a Velcro ribbon, and hence one or more fingers of a user'shand, to back surface in a manner similar to that discussed above. Thecuff can be rotationally adjusted to improve the custom-fitting of thesecuring structures for different users.

Alternatively, in some embodiment, a combination of some of the abovesecuring elements can be utilized.

Further, the above securing elements can be employed in connection withother electronic devices, such as mobile phones, personal digitalassistants (PDAs), and handheld musical devices.

In some embodiments, a computational device according to the teachingsof the invention allows a user to calculate a pay-off amount of a givenloan, e.g., at a date before the end date of the loan. By way ofexample, such a pay-off amount is typically requested by a lender when aborrower is paying off the loan before the loan's maturity date, forexample, due to refinancing, selling a property or simply paying off aloan before its final date. By way of example, FIG. 14 schematicallydepicts an exemplary computational device 128 according to such anembodiment having an interface 130 which comprises a plurality ofbuttons 132 a, 132 b, 132 c, and 132 d that are associated with amonthly payment, an amount, an interest rate, and a duration of a loanin a fashion similar to that discussed in connection with the previousembodiments. Further, similar to the other embodiments, the interface130 also includes a keypad 134 and a display 136. In this embodiment,the interface 130 further includes buttons 138, 140, and 142 labeled,respectively, “Start Date,” “End Date,” and “Today.” The buttons 138 and140 can be employed by a user to enter the start date and the end dateof a loan, respectively, in response to prompts provided in the display136. The button 142 can be used to enter a date (e.g., current date) atwhich a pay-off amount of a loan is desired. Further, a collection ofbuttons 144 enables a user to move the data entry cursor on the displaywhen entering certain data types, e.g., start or end dates of a loan.The interface further includes a button 132 e, labeled “PYF,” which canbe invoked so that the device would calculate and present the pay-offamount, e.g., in a manner discussed below.

By way of example, a user who is interested in determining the pay-offamount of a loan at a given date prior to the end date of the loan canutilize buttons 132 b, 132 d and 132 c to enter the amount, the durationand the interest rate associated with the loan, respectively.Subsequently, the user can enter the start date (or alternatively theend date of the loan) by utilizing the button 138 (or button 140). Theuser can further employ the button 142 to enter the date at which thepay-off amount is desired. In some embodiments, the device employs thecurrent date (today's date) as the default for the date at which thepay-off amount is desired. The user can change this default date, ifneeded. Subsequently, the user can press the button 132 e (“PYF”) tocause the device to calculate, and to display the pay-off amount in thedisplay 136. The mathematical relations for determining the pay-offamount are known. By way of example, the instructions for implementingsuch mathematical relations can be programmed and stored in a memorymodule of the device (e.g., the memory 36 shown in the exemplaryarchitecture shown in FIG. 3 above) to be executed by a processor (e.g.,the processor shown in FIG. 3) in response to request by the user. Suchmathematical relations can also take into account a penalty, if any, forpaying off a loan prior to its maturity date.

In some embodiments, a computational device of the invention can includea calendar interface element that allows a user to enter a date (or lookup the day of the week corresponding to a given date), e.g., to select adate (e.g., start date of a loan) from the calendar or determine thecalendar date of the end of the loan. For example, FIG. 15 schematicallydepicts a device 146 according to another embodiment of the inventionthat includes an interface 148 having buttons 150 a, 150 b, 150 c and150 d that are associated, respectively, with the monthly payment, theamount, the interest rate and the duration of a loan, as well as akeypad 152 that functions in a manner discussed in connection with theprevious embodiments. Moreover, similar to the previous embodiment,buttons 154, 156 are associated, respectively, with the start date andthe end date of a loan, and the button 158 allows a user to enter anydesired date (e.g., current date). The button 160 is associated withobtaining the pay-off amount of a loan at the date entered via thebutton 158, e.g., in a manner similar to that discussed above. Theexemplary device 146 further includes a display 164. In addition, theinterface includes a calendar 162 presented in a portion of the display164 that can be utilized to enter a date, e.g., the start or end date ofa loan. For example, upon pressing the button 154, the device an promptthe user to input the start date of a loan by presenting the message“Start Date” in a portion of the display associated with the calendar.The user can then utilize the buttons 166 to navigate through thecalendar to select the month and the day corresponding to the start date(of course, in many embodiments, the user still has the option of usingthe keypad to the enter the start date). Similarly, the calendar can beutilized to enter the end date (button 156) or the date at which apay-off amount associated with a loan is needed (button 158). Theinstructions for implementing known algorithms for calculating thecalendar as well as those for presenting it in the display of the devicecan be stored in a memory module of the device to be utilized by thedevice's processor. Although the calendar feature is discussed inconnection with a particular embodiment, it can also be implemented inother embodiments, such as those described above.

Further, in some embodiments, the device can provide a user with a sumof interest payments for a loan payable during a period from the loan'sstart date up to a given date. This enables a user to determine how muchinterest she has to pay for a loan up until the end date of the loan.This allows a user to compare, e.g., two or more loans based on thetotal (or partial) sum of interest payments required for each loan. Byway of example, FIG. 16 schematically shows a computational device 168according to such an embodiment, which is similar to the above device128 (FIG. 14) except that its interface also includes a button 170(e.g., labeled as “INTSUM”) that can cause the device to calculate sucha sum of interest payments after entry of the relevant loan parameters(e.g., loan amount, loan duration, and the interest rate) as well as thestart date (or end date) and the date at which the sum of interestpayments is desired (in some embodiments, a button labeled “today” canbe provided for entering this date, with the current date utilized asthe default date).

In some embodiments, a computational device of the invention isconfigured to allow storing information regarding a number of loans(e.g., loan amount, interest rate, duration, monthly payment, and/orstart/end date) in its memory. Each loan can be assigned a tag, forexample, in the form of a string of alphanumeric characters (e.g.,lender/clients names, etc), to distinguish it from other stored loans.By way of example, FIG. 17 schematically depicts a computational device200 according to one such embodiment having a user interface thatincludes a “SAVE” button 202 whose invocation prompts the user to entera tag for a loan whose parameters have been entered by the user and/orcalculated by the device.

A computational device of the invention, such as those discussed above,can be configured to communicate with another device or a computer, forexample, by employing known wired or wireless communication protocols.This will allow, e.g., bi-directional transfer of information on loansbetween the device and other devices or computers.

In some embodiments, a computational device of the invention can beutilized for financial planning. For example, as discussed above, insome embodiments, the device can allow a user to determine the maximumloan amount for which the user can qualify. In some embodiments, thedevice can allow a user to add the monthly cost of borrowing (e.g., onecalculated by utilizing the device) to other financial obligations(e.g., tax and insurance) to determine if she can meet all of herfinancial commitments if she proceeds with obtaining the loan. This willallow the user to decide if she can meet all her financial burdens inaddition to the loan's monthly payment. In some cases, in order tofurther help the user in assessing the financial burden associated withobtaining the loan, the device can provide the yearly property taxassociated with purchasing property. For example, the device can beprogrammed to provide such information based on the price of a piece ofreal estate in response to the entry of the postal zip code of the realestate.

Those having ordinary skill in the art will appreciate that variouschanges can be made to the above embodiments of the invention withoutdeparting from the scope of the invention.

1. A handheld electronic device, comprising: a body sized and shaped forholding by one hand of a user, a user interface comprising a pluralityof buttons for operating said device, and at least one securing elementcoupled to said body and adapted for engagement with at least one digitof the user's hand for secure holding of the body so as to allow theuser to operate a user interface of said device with one or more otherdigits of that hand, wherein said securing element comprises a recessedwell formed on a back surface of the device, and a rotationallyadjustable cuff surrounding a perimeter of said well substantially flushwith said back surface.
 2. The handheld device of claim 1, furthercomprising two rods coupled to said cuff.
 3. The handheld device ofclaim 2, wherein said securing element further comprises a hook-and-loopfastener engaged at each end to one of said rods.
 4. A handheldcomputational device, comprising a body sized and shaped for holding byone hand of a user, a processor disposed in said body, and a userinterface, comprising: n buttons each associated with a variable in amathematical equation defining a relation among n variables, whereinn>=2, and a display, wherein any (n−1) subset of said buttons can beselected to enter values corresponding to variables associated with saidbuttons in said display, and the remaining n^(th) button can be selectedto cause the processor to calculate a value for the variablecorresponding to said n^(th) button from the mathematical relation, andbased on the entered values of the other variables, and to effectpresentation of said calculated value in said display, at least onesecuring element coupled to a surface of said body and adapted forengagement with at least one digit of a user's hand for holding saiddevice body so as to allow operating said buttons by one or more ofother fingers of said hand, wherein said securing element comprises arecessed well formed on a back surface of the device, and a rotationallyadjustable cuff surrounding a perimeter of said well substantially flushwith said back surface.
 5. The handheld computational device of claim 4,further comprising two rods coupled to said cuff.
 6. The handheldcomputational device of claim 5, wherein said securing element furthercomprises a hook-and-loop fastener engaged at each end to one of saidrods.
 7. The handheld computational device of claim 4, wherein saidmathematical relation comprises a loan equation characterized by any ofa simple or compound interest.
 8. The handheld computational device ofclaim 7, where four of said buttons are associated, respectively, withan amount, an interest rate, a duration and a monthly payment associatedwith said loan.
 9. A handheld computational device, comprising a bodysized and shaped for holding by one hand of a user, a processor disposedin said body, a user interface, comprising: a plurality of functionalbuttons each associated one of a plurality of variables in amathematical equation defining a relationship among said variables, anda display, wherein in response to selection of any of said buttons by auser, said processor effects presentation of one or more prompts in saiddisplay to invite the user to enter values for variables associated withbuttons other than that selected by the user, and wherein upon entry ofthe last variable, said processor calculates a value for the variableselected by the user and presents said calculated value in the display,at least one securing element coupled to a surface of said body andadapted for engagement with at least one digit of the user's hand forholding said device body so as to allow operating said buttons by one ormore of other fingers of said hand, wherein said securing elementcomprises a recessed well formed on a back surface of the device, and arotationally adjustable cuff surrounding a perimeter of said wellsubstantially flush with said back surface.
 10. A handheld electronicdevice, comprising: a body sized and shaped for holding by one hand of auser, a user interface comprising a plurality of buttons for operatingsaid device, and at least one securing element coupled to said body andadapted for engagement with the user's hand so as to allow the user tooperate the device with that hand or the other hand, wherein saidsecuring element comprises a recessed well formed on a back surface ofthe device, and a rotationally adjustable cuff surrounding a perimeterof said well substantially flush with said back surface.